[Feat] v.in.pdal: Warn or error when max category num is reached

[wenzeslaus]

Is your feature request related to a problem? Please describe.

Lidar point clouds can have many points, esp. when combined from multiple tiles.

Describe the solution you'd like

v.in.pdal should warn or end with an error when maximum category number is reached.

Additional context

Unused variable in #2160 suggests that the check is missing.